The use of hook and loop fastener devices in consumer and industrial applications is widely known. Examples of such applications include disposable hygiene absorbent articles such as diapers, disposable garments such as surgical gowns, and the like.
In general, a hook and loop fastener device comprises a hook component and a loop component. The hook component includes a plurality of hook-shaped members anchored to a base material. The loop component includes a plurality of upstanding loop members projecting outwardly from a backing material. The hook-shaped members are designed to engage the loop members in order to provide a strong mechanical bond there between. The hook members and the loop members can typically be engaged and disengaged repeatedly.
However, when the hook and loop fastener device is intended to be used in a disposable hygiene absorbent article or a disposable garment, a low cost loop component, which adequately functions to provide a resealable mechanical closure for a limited number of applications, is desirable. There is no need for the loop component of a disposable article to possess long term capability for repetitious engagements and disengagements with the hook component because such articles only have a short life span. However, the loop component used in conjunction with the hook component should provide a relatively high peel strength, and a relatively high shear strength, i.e. it should secure closure for a limited number of use cycles.
There are a variety of loop materials available. Typical loop materials include knit or nonwoven fabrics laminated to a layer of film for support. These loop materials are typically processed on diaper lines by unwinding the material from a roll, applying adhesive to the back, film side of the loop material, feeding the material over a perforated metal cylinder which holds the material in place with vacuum suction, cutting the material in strips as it is held against the cylinder and applying the strips to diaper backsheet material that is fed in parallel through the diaper assembly line.
Polypropylene is preferred for production of nonwoven materials for diaper applications due to their relatively low cost, soft feel, availability, and ease of processing. For nonwoven loop materials it would be desirable to eliminate the use of a film support layer in order to further reduce the cost and improve the softness and flexibility of the loop material.
However, several problems have been encountered which have limited the use of nonwovens for use as loop fastening materials. These will be discussed in turn.
Typical nonwoven materials are too air permeable. Such high permeability materials cannot be held in place effectively during the strip cutting operation on the typical existing diaper line vacuum cylinders. In order to use such highly permeable materials, extensive modification to the vacuum cylinders and associated equipment would be required.
Typical polypropylene based nonwovens are susceptible to compression. When nonwoven loop materials are wound into rolls and stored for a period of time, the loop regions can become permanently compressed. When a roll of nonwoven loop material is unwound, processed on the diaper line and pieces are cut and attached to the diaper backsheet, the loop may be so flat as to no longer to be useful as an effective fastening material.
The nonwoven fibers and filaments must be bonded together to secure the structure together as well as to leave regions of unbonded fibers or loops available for fastening with a hook counterpart. If an insufficient percentage of the planar area of the nonwoven is bonded together, nonwoven fibers can be easily pulled free from the structure upon retraction of the hook when opening the fastener. If too high a percentage of the planar area of the nonwoven is bonded together there is insufficient loop fiber available for hook engagement and the fastening performance is too low. In addition, the bonding pattern has a large impact on the ease of hook engagement and therefore the fastening performance.
There is a need for low cost nonwovens for use as a loop fastening material for use in hygiene applications such as diapers that overcome these problems.